Claims:WE CLAIM:

1. A process for removal of Ammoniacal nitrogen and Cyanide content in cyanide effluent comprising:
a. maintaining the pH of the effluent (1) at 11;
b. feeding the effluent to ammonia stripper (2) at bottom temperature of 105°C to achieve ammoniacal nitrogen content of less than 50 ppm;
c. adjusting the pH of the effluent (3) in the ammonia outlet stripper between 4 to 5;
d. feeding the effluent to cyanide (CN) stripper (4) at bottom temperature of 102°C to achieve CN content less than 20 ppm;
e. adjusting the pH of the effluent in the cyanide (CN) Outlet (5) between 10 to 12;
f. treating the final effluent obtained in step (e) in Continuous Column Ozonation (6) with Ozone in continuous bubble packed column achieve CN content less than 0.2 ppm.

2. The process as claimed in claim 1 wherein in step (a) pH is maintained by using Caustic lye.

3. The process as claimed in claim 1 wherein in step (b) ammoniacal nitrogen content is reduce to less than 20 pm.

4. The process as claimed in claim 1 wherein in step (c) the pH of the effluent in the ammonia outlet stripper is achieved using sulfuric acid.

5. The process as claimed in claim 1 wherein in step (d) the CN content is in the range of 5 to 20 ppm.

6. The process as claimed in claim 1 wherein in step (e) pH is maintained by using Caustic lye.

7. The process as claimed in claim 1 wherein in step (f) the CN content is in the range of 0 to 0.2 ppm.

8. The process as claimed in any of preceding claims is applied in the effluent treatment of tanneries, agriculture, textile industries, pharmaceutical industries and chemical industries.

9. A process for removal of Ammoniacal nitrogen and Cyanide content as claimed in claim 1 wherein in step (f) wherein the packed bubble column consist of glass packing of 2-3 mm size.
, Description:FIELD OF INVENTION
The present invention relates to a process for Removal of Ammoniacal nitrogen and Cyanide content in industrial effluent.

BACKGROUND OF INVENTION
Waste waters from industrial operations, transport many chemicals that have adverse effects on the environment. Various chemicals leach heavy metals which would otherwise remain immobile. The chemicals and heavy metals may be toxic and thus cause aquatic and land biota to sicken or die. Most waste-water processing technologies that are currently available or are being developed emphasize the removal of the chemicals or heavy metals. As an environmentally protective measure, the Environmental Protection Agency (EPA) has placed rigorous limitations on the permitted cyanide concentrations levels in industrial wastewater effluent streams. Proper treatment of this wastewater is crucial for both environmental and economic reasons.

ETP (Effluent Treatment Plant) is a systematic process for treating the industrial waste water for its reuse or safe disposal to the environment. The system of effluent treatment plant is highly depending on industry and site. Untreated effluent standards and treated effluent standards are important parameters taken into consideration in process of wastewater treatment plant design. Also coming to selection treatment process, it involves consideration of treatment efficiency, cost and reliability.

“Recent Development in Ammonia Stripping Process for Industrial Wastewater Treatment” by Lennevey Kinidi in Hindawi International Journal of Chemical Engineering, 2018 highlights the recent development of ammonia stripping process for industrial wastewater treatment. In addition, this study reviews ammonia stripping application for varied types of industrial wastewater and several significant operating parameters. The disclosure is limited to ammonia stripping treatment and its application for industrial wastewater treatment. Typically, it is carried out with air which requires high diameter column which will eventually increase the initial cost of equipment. Ammonia losses will be higher which may lead to environment pollution also. Reactive scrubber will be required to scrub Ammonia which will increase the cost of process.

Raboni et al. “Experimental plant for the physical-chemical treatment of groundwater polluted by Municipal Solid Waste (MSW) leachate, with ammonia recovery” (2013) investigated the efficiency of the ammonia stripping technique for remediation of groundwater polluted with leachate. In the study, polyelectrolyte, sodium hydroxide, and iron (iii) chloride were added for the coagulation-flocculation and sedimentation processes at pH higher than 11. The system also comprised of a heater to heat the wastewater at 38°C and ammonia recovery via absorption with sulphuric acid. Lastly, the effluent was neutralized after adding sulphuric acid. As a result, they found that the ammonia stripping system for groundwater polluted with leachate displayed removal efficiency of 95.4% with initial ammonia concentration at 199.0 mg/L.

EP2559667 relates to a method and system for the treatment of wastewater containing persistent substances. In this method, fig 1 describes NH3 stripping performed by an NH3 release means 11 and an NH3 gas cooling means 12. In the NH3 release means 11, the wastewater is heated to about 90°C or higher by, for example, a heat exchanger using excess steam as a heating medium, the pH of the wastewater is adjusted to 10 or higher by adding an alkaline agent such as NaOH or Ca(OH)2, and gas such as steam or air is introduced into the wastewater to strip NH3. Typically, it is carried out with air which requires high diameter column which will eventually increase the initial cost of equipment. Reactive scrubber will be required to scrub Ammonia and HCN which will increase the cost of process.

To overcome above mentioned drawbacks and in order to meet an environmental quality guidelines and pollution control board regulations, there is a need to develop techno-economically viable and environmentally friendly process for treatment of effluent generated from industry.

There is a long felt need to develop an efficient effluent treatment plant that is simple, is able to bring about the chemical breakdown of the total and free cyanide and ammoniacal nitrogen in typical effluent streams.

The present invention relates to a process for reducing the Ammoniacal nitrogen and cyanide content in the industrial effluent.

The present inventors have surprisingly developed a cost effective process for removal of ammoniacal nitrogen and cyanide content from cyanide effluent using continuous stripper in series.

The present inventors have found a cost effective manner through the arrangement of the following component in the Effluent treatment plant (ETP).
1. Continuous ammonia stripper;
2. Ammonia Outlet stripper;
3. CN stripper;
4. Cyanide Outlet stripper;
5. Ozonation treatment column.

The present invention provides the following advantages:
1. Cost effective
2. Easy process
3. Plant Sustainability of main product.
4. No extra effluent generation
5. Recovery and recycling of ammonia and cyanide gases.

The present inventors have surprisingly developed a process for Removal of Ammoniacal nitrogen and Cyanide content from cyanide effluent that is cost effective and at the same time complies with the stringent effluent Discharge norms.

OBJECTS OF THE INVENTION
It is an object of the present invention to provide a cost-effective process for Removal of Ammoniacal nitrogen and Cyanide content from cyanide effluent.

It is another object of the present invention to provide a process for Removal of Ammoniacal nitrogen and Cyanide content from cyanide effluent using continuous strippers in series followed by continuous column ozonization.

It is another object of the present invention to provide a process for Removal of Ammoniacal nitrogen and Cyanide content from cyanide effluent that complies with the stringent effluent discharge norm.

It is yet another object of the present invention to provide a process for Removal of Ammoniacal nitrogen and Cyanide content from cyanide effluent that is sustainable and meets disposal guidelines & norms.

SUMMARY OF THE INVENTION

According to an aspect of the present invention there is provided a process for reducing or removing ammoniacal nitrogen and cyanide content in an industrial effluent.

In another aspect the present invention provides a process for removal of Ammoniacal nitrogen and Cyanide content, with reference to figure 1 comprising
1. maintaining the pH of the effluent (1) at 11;
2. feeding the effluent to ammonia stripper (2) at bottom temperature of 105°C to achieve ammoniacal nitrogen content of less than 50 ppm;
3. adjusting the pH of the effluent (3) in the ammonia outlet stripper at pH 4 to 5;
4. feeding the effluent to cyanide (CN) stripper (4) at bottom temperature of 102°C to achieve CN content less than 20 ppm;
5. adjusting the pH of the effluent in the cyanide (CN) Outlet (5) at pH 11 to 12;
6. treating the final effluent obtained in step (e) in Continuous Column Ozonation (6) with Ozone in continuous bubble packed column to reduce CN content less than 0.2 ppm.

BRIEF DESCRIPTION OF THE DRAWINGS
The above and other aspects, features and advantages of certain exemplary embodiments of the present invention will be more apparent from the following description taken in conjunction with the accompanying drawings wherein:
Figure 1: Complete schematic diagram of the ETP of the present invention.
Figure 2: Continuous ozonization treatment column.
DETAILED DESCRIPTION OF THE INVENTION

The following description with reference to the accompanying drawings is provided to assist in a comprehensive understanding of exemplary embodiments of the invention. It includes various specific details to assist in that understanding but these are to be regarded as merely exemplary.

Accordingly, those of ordinary skill in the art will recognize that various changes and modifications of the embodiments described herein can be made without departing from the scope of the invention. In addition, descriptions of well-known functions and constructions are omitted for clarity and conciseness.

The terms and words used in the following description and claims are not limited to the bibliographical meanings, but, are merely used by the inventor to enable a clear and consistent understanding of the invention. Accordingly, it should be apparent to those skilled in the art that the following description of exemplary embodiments of the present invention are provided for illustration purpose only and not for the purpose of limiting the scope of the invention as defined by the appended claims and their equivalents.

It is to be understood that the singular forms “a,” “an,” and “the” include plural referents unless the context clearly dictates otherwise.

Features that are described and/or illustrated with respect to one embodiment may be used in the same way or in a similar way in one or more other embodiments and/or in combination with or instead of the features of the other embodiments.

Typically, the feed effluent contains ammoniacal nitrogen content of about 3000 ppm and Cyanide content of about 200 ppm. The present invention is directed to provide a cost-effective process to reduce ammoniacal nitrogen below 50 ppm and cyanide content below 0.2 ppm.

Thus, present invention is particularly directed to a process for reducing or removal of ammoniacal nitrogen below 50 ppm and cyanide content below 0.2 ppm, thus meeting the regulatory norms.

In an embodiment, the present invention relates to a process for removal of Ammoniacal nitrogen and Cyanide in cyanide effluent as per Effluent Treatment Plant (ETP) discharge norms using Continuous strippers in series followed by Continuous column ozonation.

In an embodiment, the composite stream to be treated usually comprises sodium cyanide (NaCN), sodium formate (HCOONa), hydrogen cyanide (HCN) and Ammoniacal nitrogen (NH3-N).
Table 1
Composite stream
Components Composition (ppm)
NaCN 161-181
HCOONa 87-107
HCN 62-82
NH3-N 2829-2949

The process according to the present invention comprises following series of steps for removal of ammoniacal content and cyanide content from the effluent and to achieve the ETP discharge norms.

Step 1: Maintaining pH of Effluent (1): Effluent pH is maintained above 11 with Caustic-lye.

Step 2: Ammonia stripper (2): After pH adjustment effluent is feed to continuous ammonia stripper at 105°C bottom temp where ammonia is stripped and less than 50 ppm, preferably in the range of 30 to 45 ppm. Ammoniacal nitrogen is achieved.
Ammonia column will be packed column with reflux provision. It will be same as distillation. It is continuous operation where 10% of cut will be removed in it to get 10-15% ammonia in top which can be reused in process. Distillation is indirect contact with the steam so no extra effluent will be generated.

Step 3: pH adjustment of effluent (3): pH of effluent in ammonia Outlet stripper is achieved between 4 to 5 using acid.

Step 4: CN stripper (4): After pH adjustment effluent is treated in CN stripper at bottom temp ~ 102°C to achieve CN content less than 20 ppm, preferably in the range of 5 to 20 ppm.
The acid is used is concentrated H2SO4. The cyanide column will be packed column with reflux provision. It will be same as distillation. It is continuous operation where 10% of cut will be removed in it to get 1-2% HCN Solution in top which can be reused in process. Distillation is indirect contact with the steam so no extra effluent will be generated.

Step 5: pH Adjustment of Cyanide Outlet stripper (5): pH of Cyanide Outlet stripper is achieved ~11-12 by Caustic lye.

Step 6: Continuous Column Ozonation (6): Finally, Effluent is treated with Ozone in continuous bubble packed to column to achieve CN <0.2 ppm.
The aforesaid steps in series are effective in terms of cost and ease of operation. The process of the present invention achieves 90% efficiency in terms of ozone; and final discharge of effluent having less than 0.2 ppm CN and less than 50 mm ammoniacal nitrogen.
Preferably the present process is a continuous process.

In an embodiment the present continuous process is carried out in packed bubble column.

The process is carried out at temperature in the range of 50°C to 150°C, preferably 50°C to 100°C, preferably 90°C to 100°C, and at atmospheric pressure.

As an embodiment of the present invention uses the effective arrangement of ammonia stripper, cyanide stripper couple with requisite pH adjustments followed by continuous ozonization for removal of Ammoniacal nitrogen and Cyanide.

According to an embodiment of the present invention, the destruction of cyanide in Cyanide effluent (to content less than 0.2 ppm) is by using Ozone in Continuous column.

As an embodiment of the present invention, the effluent pH is to be maintained above 10, preferably above 11 using caustic lye before feeding the effluent to continuous ammonia stripper. The temperature of the continuous ammonia stripper is preferably maintained at about 100 to 110 °C, preferably 105°C bottom temperature to achieve <50 ppm Ammoniacal nitrogen.

The process is carried to about 2 to 10 hours preferably, 5 to 10 hours more preferably 5 to 7 hours.

The pH of the effluent in Ammonia Outlet stripper is adjusted to pH 4 to 5 using acid for example sulfuric acid before feeding to the cyanide (CN) stripper. The temperature of the CN stripper is preferably maintained at about 100 to 110 °C, preferably at about 102°C bottom temperature to achieve CN content <20 ppm.

The pH of the effluent in cyanide (CN) Outlet stripper is adjusted to pH 11 to 12 by caustic lye before treating the final effluent with ozone in continuous bubble packed to column to achieve CN content <0.2 ppm.

The present invention employs a packed bubble (figure 2). Liquid will be charged from top and Ozone gas will be fed from the bottom. Ozone gas will pass through this sieve plate and pool of liquid where reaction will take place. So, in each section this phenomenon will occur and at bottom of the layer cyanide will be <0.2 ppm.

With reference to figure 1, the process for removal of Ammoniacal nitrogen and Cyanide content in cyanide effluent comprising:
a) maintaining the pH of the effluent (1) at 11;
b) feeding the effluent to ammonia stripper (2) at bottom temperature of 105°C to achieve ammoniacal nitrogen content of less than 50 ppm;
c) adjusting the pH of the effluent (3) in the ammonia outlet stripper between 4 to 5;
d) feeding the effluent to cyanide (CN) stripper (4) at bottom temperature of 102°C to achieve CN content less than 20 ppm;
e) adjusting the pH of the effluent in the cyanide (CN) Outlet (5) between 10 to 12;
f) treating the final effluent obtained in step (e) in Continuous Column Ozonation (6) with Ozone in continuous bubble packed column achieve CN content less than 0.2 ppm.

In an embodiment, in step (a) pH is maintained by using Caustic lye.

In an embodiment, in step (b) ammoniacal nitrogen content is reduce to less than 20 pm.

In an embodiment, in step (c) the pH of the effluent in the ammonia outlet stripper is achieved using sulfuric acid.

In an embodiment, in step (d) the CN content is in the range of 5 to 20 ppm.

In an embodiment, in step (e) pH is maintained by using Caustic lye.

In an embodiment, in step (f) the CN content is in the range of 0 to 0.2 ppm.

In the present invention the inlet and outlet concentration of Ozone in the column was continuously monitored. It was observed that no major ozone losses were observed. Based on this the present invention ETP achieves 90% efficiency.

It was observed that upto certain deviation in Cyanide (18~25 ppm) no variation in result observed.
The data is as follows: Table 2-
EXPT ID SPM-13/Q-09/50

Liquid hold up (lit) 0.8
Cyanide content (ppm) 21.07
pH 11.0
TDS (ppm) 5780
Feed flow rate (lit/min) 0.075
Ozone flow rate (lit/min) 0.5
R.T (min) 10.7
Current (Amp) 1.03
Ozone generation rate (gm/hr) 1.52
Ozone excape rate (gm/hr) 0.34
Efficiency (%) 78
Mole ratio (O3 : CN-) 6.74

Time CN- (ppm)
(hrs) Section-2
0.0 21.07
0.5 0.73
1.0 0.28
1.5 0.14
2.0 0.12
2.5 0.11
3.0 0.09
3.5 0.12
4.0 0.11
4.5 0.15
5.0 0.10
5.5 0.08
6.0 0.03
6.5 0.10
7.0 0.09
7.5 0.07
8.0 0.09
8.5 0.10
9.0 0.08
9.5 0.09
Composite analysis 0.15

The present invention ETP is clean and green technology wherein no extra effluent is generated in final discharge. Furthermore, present process involves recycle of the top concentrated/distillate mass for reuse in process.

Final treated effluent exiting in the present invention consists of dissolved oxygen which is good for release to environment.

Typically, the effluent to be treated contains ammoniacal nitrogen content of about 3000 ppm and Cyanide content of about 200 ppm. Advantageously, the final discharge of effluent according to the present process contains <0.2 ppm CN (i.e. 0 to 0.19) and Ammoniacal nitrogen is less than 50; preferably in the range from 10 to 45 ppm, preferably less than 20 ppm.

The present invention is useful the agriculture industry. In some embodiments, the process finds application for the removal of ammoniacal nitrogen in the effluent of tanneries, textile industries, pharmaceutical industries and chemical industries.

According to an embodiment of the present invention the removal of ammoniacal nitrogen and Cyanide content from cyanide effluent using continuous stripper in series followed by Continuous Column ozonation and to achieve the norms as per ETP:
1. Stripper column is designed to get the higher concentration NH3 and HCN content in top distillate.
2. Top product of the ammonia column will be 10-15% NH3 and 1-3% HCN vs Feed is having ~ 0.25% ammonia and 0.02 to 0.05% Cyanide solution.
3. Recycle of the top concentrated/distillate mass for reuse in process.
4. Indirect contact of steam is given in both the strippers which is different in compared to steam/air stripping. Normally, stripper for this column is designed for air or direct steam strippers. In the present invention strippers are in indirect contact.
5. Stripper columns diameter is less compared to Conventional air/steam strippers. Air stripper and steam strippers requires higher diameter column. As the present stripper column is a distillation stripper column, no extra addition stream is used so diameter requirement will be less.
6. With the process of the present invention, in treated effluent the Ammoniacal nitrogen content is less than (<) 50 ppm and CN content is less than (<) 0.2 ppm.
7. It is clean and green technology wherein no extra effluent during the process.
8. Cost effective process in comparison to other conventional methods.

The invention is further illustrated by working examples as detailed below. The examples are meant for illustrative purposes only and are not meant imply restriction to the scope of the disclosure in any manner.

EXAMPLES:
Example 1
Composite stream: Ammoniacal nitrogen and Cyanide content in cyanide effluent
Table 3

NH3-Removal
Table 4
Stream Qty Analysis (PPM) Parameters Remark
Plant 185 KLD NH3-N 2400
CN 165
Feed 800 gm NH3-N 1900 to 2200
CN 100 to 150
pH 12 to 12.5
Top Cut 80 gm NH3-N 14000 Temp: 93 to 95 deg C
Press.: Atm Average
CN 40 Average
pH 11 to 12.5
Bottom mass
(This stream will go to HCN stripper) 708 gm NH3-N 55 to 124 Temp: 99 to 100 deg. C
Press.: Atm
CN 140 Average
pH 11.5 to 13

CN-Removal
Table 5
Stream Qty Analysis (PPM) Parameters Remark
Plant 185 KLD NH3-N 2400
CN 165
Feed 600 gm NH3-N 30 to 70
CN 240 to 265
pH 4 to 6.5
Top Cut 62 gm NH3-N 159 Temp: 93 to 95 deg C
Press.: Atm Average
CN 1600 Average
pH 7 to 8.5
Bottom mass
(This stream will go to ion exchange towerr) 532 gm NH3-N 20 to 90 Temp: 99 to 100 deg. C
Press.: Atm
CN 6 Average
pH 4 to 6

Continuous Column ozonation (figure 2): components: (1) Oxygen Cylinder; (2) Flow meter; (3) Ozonater; (4) Ozone in Oxygen Gas input to column; (5) Packed column; (6) Effluent in with 5-20 ppm cyanide; (7) Vent gas to Ozone destructor; (8) Final effluent outlet and (9) Final effluent collection vessel

In Figure 2, Oxygen from oxygen cylinder (1) is fed to ozonater (ozone generator) (3) at control rate. From ozonater outlet, with 6-12% of ozone concentration, ozone O3 is fed (4) to the continuous packed column (5) from bottom. From top of the column, the final effluent (6) with cyanide content 5-20 ppm is fed. Both the streams are fed in column in counter current manner. Final Liquid (elute) (8) will be discharged from the bottom of the column having cyanide content <0.2 ppm to collection vessel (9). And vent gas leaves (7) from the top of column which can vented in atmosphere via ozone destructor.

Residence time is kept 10-15 min with respect to feed effluent.

Laboratory packed column consist of 2-3 mm glass packing column.

Typical dimension of lab packed column is as per following.

Table 6

It is to be understood that the present invention is susceptible to modifications, changes and adaptations by those skilled in the art. Such modifications, changes, adaptations are intended to be within the scope of the present invention.